At a loss troubleshooting leaves

[Legalcdn]

I have looked at all deficiencies with pictures.

Finished 5 weeks of flower. Bit of strange yellowing progressing to brown/red. It started week 4 and has progressed. It was the same last grow with same strain (Malawi). All at the top canopy. I am now at the start of week 6.

Environment:

EB Strips 220w (3000 and 3500k).
5x3.5ft space
Vent Fans above and below canopy. RH is about 55%.
Coco DTW using Jacks 5-12-26, cal-nit, epson salt. PPM is 750 total with tap. 3gr jacks, 2.5gr cal-nit, 1gr epson. Hydroton rocks 1 inch on bottom and 1 inch on top (been washed good).

Elemental NPK: 135-41-190, 125cal-70mag.
PH is 6.0-6.2. It drifts from start of 5.8.
Temps constant at 26C (77f)
About 18inch distance of lights to canopy. I see the same issue in the middle and on the fringe of lights.

LEDs sometimes need extra cal-mag.
Looks like phosphorus issue (currently 48ppm elemental) or immobile nutients?

Hand watering 2 liters daily. I get 10-20% runoff.

At loss on where to look next..

 

[maryjaneismyfre]

Measure your PH and EC of run off and compare to what you are feeding, start from there.. I'd drench the soil with beneficial microbes like trichoderma and bacillus immediately and enzymes if you can get, it looks like you have funny microbial stuff happening in root zone..What is your pot volume, 20% of runoff on handwater is too much, may be overwatering..

 

[Legalcdn]

My next move is to capture runoff and analyze. I am in coco so i am not adding extras to my mix. I will increase watering to 3x a day at 1/5th of gallon (800 ml each watering) to flush out potential salt build-up. My buckets have 10 liter capacity (2.75gal). Coco/perlite needs to stay about 90% saturated. Coco was double buffered with cal-mag.

going to boost NPK to 135-82-192 with cal mag at 125-80.

 

[...CR500AF...]

Ya i would not increase any food or watering's yet.
I would be looking at PH and how far is the LED away from the plants they need more space then people usually think.
Just a thought, I will wait see how it turns out for ya, I hope you find the problem soon.

 

[...CR500AF...]

Hmmm I did not see the ph that you wrote out 18 inch's for the light seems a little tight but with that said it should be effecting all the others as well but i see it is not. So i guess i would be stumped right along side you,sorry for not seeing that the first time.

 

[maryjaneismyfre]

Coco perlite, id water half that handwater, once a day to get a pulse of fresh air in the medium with a flood in the medium and drain and a dryback in between, well not really dryback but more aeration of gaps in medium...I run coco perlite know how to make it perform..I'd water in with peroxide now, to stop any funny stuff that likes growing in very wet or anerobic medium and add trich and bacillus after..its got the look to me when I keep a plant in coco too wet, but yer runoff amount verse pot volume, runoff EC and PH will give you a clearer picture..if you are getting 20% of 2L a day in runoff on a 10 L pot, handwater in coco/perlite, you are overwatering..Thats 400ml for a ten L pot, 4% of volume.
I had guys handwatering hundreds of plants for me daily, for years, on a commercial scale, I'd aim for 1% pot volume total runoff over hundreds of plants to drain, and when I was getting that day in and day out the plants would love life and pots moisture would have reached its happy metronomic daily cycle and I'd maintain that all the way to the bank..I mean end..these days I have soil probes and monitoring software and stuff and bosses who like get get us shiny toys and Im no longer the boss, but considerably scaled up and still coco/perlite and I aim for a daily hover between 50% after waterings to 25% sleeping and I push easy g/w quick cycle with my eyes closed as I did on a handwater back then and better than industry ave per m2 Ghouse. almost double actually..im no slouch nor new to this..these days I have tens of thousands of plants at any given stage in flower under drip, which is completely different ratios of run off and feed etc, as one must allow for wicking across a medium, plants prefer a handwater but can't handwater thousands nevermind a day..LOL..Flood and drain my favourite but setting up this scale is a nightmare..but ja I'd put my money on anaerobic medium and possible the cause being overwatering..but that said there are many factors always at play..its a guess from a picture from other side the planet, take with pinch of salt.
Tomorrow water 10% of pot volume, take note of run off volume to pot volume and EC, PH, if run off over 2% of pot volume and PH lower than feed PH, the more lower the more likely funny microbes doing no good cuz the environment down there in medium suits them and not you.

 

[Legalcdn]

Maryjaneismyfire, thanks for suggestions. The word that helped was dryback. Seems too much dryback.

Ran 6 liters thru each plant. 500 Ppm and 6.1ph of water.

plant 1 runoff: ph stable at 6.2. Started at 2100ppm and finished water at 800ppm.

plant 2 runoff: ph stable at 6.25. Started at 2200ppm and finished water at 1600ppm.

Pretty safe to say salts were accumulating. When i checked runoff 2 days ago, the runoff was 5%.

i will run more 500ppm water tomorrow until stable at 500-600ppm. Maybe flora kleen to eat up the salts.

moving to 3 feeds of 800ml per session in a couple days.

 

[maryjaneismyfre]

Your gals turn for the better..?

 

[Legalcdn]

They did. I battled high ppm ranging from 1800-1200ppm for 3 days. I used DIY clearex (dextrose, sucrose) twice and lowered ppm watering to 400-600ppm. Stabilized at 650ppm runoff. Now i have autowatering DTW going that should stop salt build-up.

the PPM was constant at 750-800 before issue but it was accumulating day by day.

thanks for help.
Not a total loss when you gain knowledge/experience from issue. Now i have learned about symptoms of salt excess.

 

[maryjaneismyfre]

Yeah bro it was over watering, or underwatering, the runoff test was going to tell you which direction to head in.. Taught to me by very successful hydroponics vegetable farmers 20 years ago..works like a charm!